Update test style to separate structure and numerical data

[lazyoracle]

Describe the missing feature

Current tests have a coupled design where the pickle files store the structure and numerical data as a regression/historical test. This becomes difficult to maintain in the long run and also difficult to change (in the rare cases when we need to).

Describe the solution you'd like

We want to separate the structure and the numerical content and possibly also get rid of pickle files if possible. Also, we should only check the structure when it is part of the contract or API (Ref: Programming by Contract for Python)

Describe alternatives you've considered

• Storing everything in pickle files in the same repo
• Storing everything in pickle files in another repo
• Storing this binary data in some cloud server (if it very rarely changes)

Additional context

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